Multiple blade variable pitch fan



ec 9, 1952 E. M: TURNER MULTIPLE BLADE VARIABLE PITCH FAN 2 SHEETS-SHEET 1 Filed March 12, 1951 INVENTOR. E9715)" M. fl/e/vse,

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MULTIPLE BLADE VARIABLE PITCH FAN Filed March 12, 1951 2 SHEETSSHEET 2 III II INVENTOR. E975? M. 722N542,

ATTOQNEX Patented Dec. 9, 1952 UNITED STATES PATENT ()FFI-CE MULTIPLE VARIABLE PITCH FAN Estey M. Turner, Arcadia, Calif.

applicationmarchlz, 1951, SerialNo: 2151081 Claims. I

This invention relates to air impellers and is a continuation-in-part of application, Serial No. 714,447, heretofore filed by me on December- 6, 1.946.- As in that earlier application, the invention has particular reference to automobile radiator cooling fans.

The conventional typeof radiator cooling fan commences to circulate air through the radiator the moment the automobile motor isstarted. This is objectionable for the reason that theinitial heatingof the motor thereby is delayed; It is, in View of the foregoing, an object of the present invention to provide an air circulating mechanism which, while the motor is still cold will not impel air against the radiator but will, as the motor gradually commences toheat" up, increasingly direct the air now thereagainst.

In order so to control the direction of the airflow, it is necessary toprovide means for varying the'pitch of the fan; In this connection, certain difficulties are encountered; It is found that a certain force or combination of forces which for convenience of description-may be termed the centrifugal torque,- exerts increasing pressureagainst the ordinary fan blades in proportion to speed increases of the fan, tending toturn the blades on their longitudinal axis into neutral position.

It is afurther'objectof the inventionto provide, in an air impeller, a blade combination which is designed and constructed to neutralize the force exerted against the' bladesby the cen trifugal torque, to the end that any desired change in the pitch of the fan blades may be. conveniently and smoothly elf'ected withoutexertion ofv any appreciable. amount of power.

Illustrative of" the invention, I have hereinafter described in detail: a fan structure including twin blades, the units of which are. spaced about or on opposite sides of the. axis of rotation of the blades in such-relation to each. otherand to' the: axis of the blade units that. the forces tending to oppose or impede axial rotation of the-blade units to vary the pitch thereof while: the fan is in motion will be, counter-balanced or nullified by the relative position and angular relation of the blade units. In addition, it is found important to be able rotatably to adjust the units of each blade on their common longitudinal axis as may be required further to neutralize the effect of the centrifugal torque. Means such as counter-weights or similar well known compensators may also be embodied in the blade units to insure more complete neutralization of the efiect of the centrifugal torque forces, if found necessary or desirable.

These and other objects of the invention will be better understood from thefollowing detailed description thereof and by referring to the accompanying drawings in which a preferred form of the invention is illustrated.

In the drawings:

Fig. 1 is a front view of a device embodying the invention and with parts thereof broken away for the sake of clearness;

Fig. 2 is a substantially corresponding side elevational' view taken mostly through the center of Fig. 1;

Fig. 3 is a fragmentary plan view, on a larger scale, showing an important feature of the invention; and

Fig. 4 is a cross sectional view taken on line 4 of Fig. 3.

The structure of the invention, inthe form illustrated inthe drawings, comprises an annular casing consisting of two identically shaped half-positions I, 2 The two parts of the casing are shown perforated to receive bolts 3, by means of which the casing is rigidly clamped in position on the hub 4- 0f the fan.

Within the central passage 5 of the casing is slidably seated a cylindrical member 6, the surface of which has been machined to-provide four flat surfaces 6*, at right angles to each other and of the same distance from the axis of the casing.

Four annular bosses project radially from the body of the casing and the axes of these bosses intersect the axis of the central passage 5; The inner surfaces of the bosses are shaped to receive and rigidly to support ball or roller bearing races 1.

An impeller or fan consisting of four twin blades 9, It is held rotatable within the bosses of the casing in the following manner. A- sub-- stantially cone-shaped hub H is made with a shank l2, which is rigidly anchored within a conical sleeve is, as by means of splines it, and this sleeve is made with a flange 5, to the outer surface of which the twin blade units 9, It are rigidly clamped. Illustrative of such clamping means, the end of the shank I2 is shown threaded to receive a nut l6, and a lock washer H is placed under the nut to prevent accidental dislocation thereof.

The conical hub H and the sleeve 13 are symmetrically shaped and positioned relative to the race 7 to form therewith bearings-for. balls or rollers i3 by means of which the blade is held rotatably locked in position within the bosses.- t is to be understood that all four bosses are identically'fitted to support the four blades of the fan.

'Ihe member 6 is axially perforated to receive and hold a control rod 20, by means of which the member is movable axially. Four equidistant, radially projecting pins 2! are seated in the member 5 and extend through perforations of four- 3 actuating links 22, which latter are seated for partial rotation within recesses in the fiat surfaces 6*.

A second set of pins 24 extend from the links 22 into each of the four blade hubs II. From this, it is seen that axial movement of the control rod and the member 6 is translated into rotating movement of the fan blades to change the pitch thereof.

The fan blades 9, it) are for the purposes of the present invention of a special twin shape, as will be more particularly explained presently. Each blade is made from two identical strips of sheet metal which are bent at right angles, substantially as indicated in the drawings, and they are for the sake of rigidity riveted in position on similarly shaped anchoring brackets 29, 30. Each assembled twin blade is thereupon placed under the threaded nut is and rigidly clamped in position.

The conventional type of single fan blade is, due to the great, difference of the principal moments of inertia of the blade sections, subject to high centrifugal couples tending to twist or turn the blade into neutral position. Besides, such single blades offer little resistance against torsional as well as bending vibrations.

The twin blades of the present invention are designed to overcome these drawbacks, and it is found that they can be made wider than the type of blades ordinarily used. The two units of each blade may have either no stagger or a desired amount of stagger. A substantial stagger gives a useful over-balance which can overcome the average aerodynamic moment and also increase the projected width cf blade area. Besides, the principal aXis of minimum moment of inertia of the twin blades is arranged at such an angle relative to the plane of rotation that the centrifugal torque is zero at any pitch.

However, as above suggested, the fan may also be over-balanced by means of counter-weights placed on the anchoring brackets 29, 3e, substantially as indicated at 3 l.

As above stated, it is the object of the invention to so control the pitch angle of the fan that the air flow will be directed away from the radiator until the latter commences to become heated,

whereupon the air flow gradually is directed towards and through the radiator. Experience proves that the above described twin blade construction and arrangement will produce this important, highly effective result. Any conventional thermostatically controlled mechanism may be provided to move the rod 29 and the member 6 for the purpose of such pitch variations, and such mechanism is, for this reason, not illustrated in the drawing.

As above stated, it is important to employ two separate blade units, such as illustrated in the drawings, for the reason that this construction makes it possible rotatively to adjust the units on their common longitudinal axis as may be required more completely to neutralize the effect of the centrifugal torque.

By making the units relatively adjustable in this manner, it is also found that the angular position of one unit relative to that of the other may be correctly calculated to suit the curvature and the extent of the relative stagger of the units, to the end that the most efficient fluid impelling blade combination may be obtained.

While I have herein described preferred forms of the invention, it is to be understood that various changes and modifications may be embodied, within the scone of the claims hereto appended.

I claim:

1. In a variable pitch air impeller, the combination with a casing forming the hub of the impeller, of studs radially projecting from the axis of said casing for rotation therein, two fan blades seated for relative rotation on each of said studs to adjust the pitch angle of the blades relatively to each other to form thereon a radially directed twin blade, and means for clamping the blades of each twin blade in relative adjusted position on each of said studs.

2. In a variable pitch air impeller, the combination with a casing forming the hub of the impeller, of studs radially projecting from the axis of said casing for rotation therein, two L- shaped fan blades seated for relative rotation on each of said studs to adjust the pitch angle of the blades relatively to each other to form thereon a radially directed twin blade, and means for clamping the blades of each twin blade in relative adjusted position on each of said studs.

3. In a variable pitch air impeller, the combination with a casing forming the hub of the impeller, of studs radially projecting from the axis of said casing for rotation therein, a pair of L- shaped brackets seated for relative rotation on each of said studs to form thereon a radially directed U-shaped blade support, means for clamping said brackets rigidly in relative circumferentially adjusted position on said studs, and a blade on and radially extending from each bracket.

4. In a variable pitch air impeller, the combination with a casing forming the hub of the impeller, of studs radially projecting from the axis of said casing for rotation therein, a pair of L- shaped brackets seated on each of said studs to form thereon a radially directed U-shaped blade support, a blade unit on and radially extending from each bracket to form a twin blade, the units of each blade being relatively staggered in the direction of the airflow to bring the leading edge of the front unit somewhat behind the leading edge of the follower unit, and means for clamping said bracket in relatively circumferentially adjusted position on the studs.

5. In a Variable pitch air impeller, the combination with a casing forming the hub of the impeller, of studs radially projecting from the axis of said casing for relative rotation therein, a pair of L-shaped brackets seated for rotation on each of said studs to form thereon a radially directed U-shaped blade support, means for clamping said brackets rigidly in relative circumferentially adjusted position on said studs, 2. twin blade on each support, each of said twin blades including a blade unit on and radially extending from each bracket, and centrifugal torque resisting elements secured to L-shaped brackets.

ESTEY M. TURNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,098,306 Trautmann et al. May 26, 1914 1,463,441 Pike July 31, 1923 1,813,877 Gunn July 7, 1931 2,083,569 Larason June 15, 1937 2,316,940 Dewey et al Apr. 20, 1943 2,34 ,266 Reissner Mar. 14, 1944 

